The present invention provides a nitrogenous composition resulting from the enzymatic hydrolysis of maize gluten.
The present invention also relates to a process for the preparation of such a nitrogenous composition and to the application thereof in culture media for the fermentation industries.
This nitrogenous composition may also be used as a feedingstuff or food additive in compositions for animals.
Maize gluten is known to be a source of nitrogen in the fermentation industries and a constituent of certain foodstuffs.
However, due to the viscoelastic properties of maize gluten, it must be solubilised if it is to be used as a source of nitrogen in bioengineering processes or as a feedingstuff or food additive.
This solubilisation of gluten may be carried out by chemical means (alkaline hydrolysis or acid hydrolysis) or by enzymatic means.
For example, patent application WO 95.28850 describes a method of solubilising plant proteins by using enzymes with phytase activity in combination with one or more enzymes with protease activity, one or more enzymes with lipase activity and one or more enzymes with glycosidase activity. These enzymes are extracted from microorganisms of the Bacillus, Pseudomonas, Kluveromyces, Saccharomyces, Aspergillus type.
The mixture thus hydrolysed is then used in animal feed.
The patent EP 518.999 describes the preparation of partially hydrolysed products by virtue of a specific treatment using a particular serine protease produced by Bacillus licheniformis. These products are of interest for the preparation of foods for human consumption and particularly in infant foods as an agent which limits the allergenic capacity of the proteins of full cream milk, and on account of their properties of better digestibility.
Patent application EP 461.261 describes the preparation of particular oligopeptides by enzymatic hydrolysis of plant proteins in order to obtain a high proportion of branched amino acids and the use thereof in food preparations intended for patients suffering from liver diseases.
A process which allows the preparation of an aromatiser by enzymatic hydrolysis of a substance rich in plant proteins without having to use purified exopeptidases to take away the bitterness, whilst giving it attractive organoleptic properties, has been described in patent EP 429.760.
The possibility of using an hydrolysed of plant proteins in a fermentation medium is also mentioned in patent application WO 94.25580.
However, none of these documents indicates or suggests that a hydrolysed of maize gluten having a particular composition in terms of its phosphorus and nitrogen content, its concentration of soluble and insoluble proteins and its distribution spectrum of amino acids, may be particularly suitable for fermentation applications, particularly in the field of fermentations of microorganisms which produce organic acids and/or in animal feed applications.
The invention relates primarily, therefore, to a nitrogenous composition resulting from the hydrolysis of maize gluten, having a ratio of the concentrations of inorganic phosphorus to total phosphorus (Pi/Pt)greater than or equal to 0.05, preferably from 0.05 to 0.5, and a ratio of the concentrations of amine nitrogen to total nitrogen (Na/Nt) greater than or equal to 0.025.
The concentrations of inorganic phosphorus and total phosphorus are measured by methods known on the whole by the skilled person, such as those described below.
With regard to inorganic phosphorus, the reference method consists in extracting the mineral or inorganic phosphorus by a solution of trichloroacetic acid, forming a phosphomolybdic complex by reaction between inorganic phosphorus and ammonium molybdate, and measuring the absorbance of this complex with a spectrophotometer at a wave length of 360 nm.
The determination of total phosphorus is carried out by a method which is based on the detection of phosphorus on a plasma emission spectrometer (JY83 type from JOBIN YVON following the constructor""s specifications). A preliminary step is used, however, which consists in destroying the organic materials of the products to be determined in order to convert all the organic phosphorus to inorganic phosphorus (the total phosphorus is therefore the organic phosphorus plus the inorganic phosphorus), by mineralisation using a sulfonitric mixture.
The ratio of the inorganic phosphorus concentration to the total phosphorus concentration (Pi/Pt) is preferably greater than or equal to 0.05, preferably from 0.05 to 0.5.
The concentrations of amine nitrogen and total nitrogen are measured by known methods such as those described below.
The determination of amine nitrogen is carried out by allowing the amine function of the product to be determined to react with trinitrobenzenesulfonic acid (TNBS) in order to produce a chromophore group, the absorbance of which is measured at 340 nm.
The determination of total nitrogen is carried out according to the ISO 3188 method which involves mineralisation of the product to be determined with sulfuric acid in the presence of a catalyst, then alkalinisation of the reaction products and distillation of the ammonia liberated and collected in a solution of boric acid which is titrated with a solution of sulfuric acid.
The total protein content and the soluble protein content of the composition according to the invention are, respectively, from 20% to 80%, based on dry matter basis, and from 30% to 80%, on dry matter basis.
The term total protein content means the total nitrogen multiplied by a factor of 6.25.
The term soluble protein content means the total nitrogen multiplied by a factor of 6.25 contained in the soluble fraction which corresponds to the supernatant obtained after dispersion of the sample in distilled water and centrifugation.
Moreover, the nitrogenous composition according to the invention has a free alanine content greater than or equal to 100 mg/100 g on a dry matter basis, preferably 500 mg/100 g on a dry matter basis, a free leucine content greater than or equal to 200 mg/100 g on a dry matter basis, preferably 1000 mg/100 g on a dry matter basis, and a free phenylalanine content greater than or equal to 100 mg/100 g on a dry matter basis, preferably 500 mg/100 g on a dry matter basis.
The invention relates secondly to a process for the preparation of a nitrogenous composition resulting from the enzymatic hydrolysis of maize gluten by a particular combination of enzymes.
The maize gluten used is preferably a slurry of maize proteins obtained after grinding grains of steeped maize and after separating the germs and starch by a physical process based on the difference in density of the compounds.
Maize gluten may also be extracted from the slurry of proteins by physical separation of the centrifugation or filtration type and then resuspended in water in order to carry out the enzyme treatment according to the invention.
The process according to the invention consists in subjecting an aqueous solution of maize gluten to an enzyme treatment using at least one protease and optionally at least one enzyme selected from the group comprising a complex of endo- and exopeptidases, an enzyme complex which hydrolyses the polysaccharides of maize other than starch, a phytase and a glucoamylase.
In a first method of preparing the nitrogenous composition according to the invention, an aqueous solution of maize gluten is treated in a series of steps comprising:
introducing successively into the aqueous solution of maize gluten at least one protease then optionally a complex of endo- and exopeptidases,
allowing the enzymes to act, with stirring,
inactivating the enzymes,
optionally separating the insoluble matter,
recovering the nitrogenous composition thus obtained.
The proteases are preferably papain (for example, COROLASE(copyright) L10 sold by the company Rxc3x96HM ENZYME) and/or an alkaline protease (such as the alcalase isolated from B. licheniformis). This first hydrolysis reaction will be performed advantageously at a pH of 8.
The complex of endo- and exopeptidases will be preferably KOJIZYME(trademark) (sold by the company NOVO NORDISK). The enzyme reaction is then performed at a pH from 6 to 6.5, as will be illustrated below.
In a second method of preparing the nitrogenous composition according to the invention, said aqueous solution of maize gluten is treated in a series of steps comprising:
introducing simultaneously into the aqueous solution of maize gluten at least one protease, at least one enzyme complex which hydrolyses the polysaccharides of maize other than starch, at least one phytase and at least one glucoamylase,
allowing the enzymes to act, with stirring,
inactivating the enzymes,
optionally separating the insoluble matter,
recovering the nitrogenous composition thus obtained.
The proteases are preferably an acid protease (for example, acid Bioprotease A sold by the company BIOCON) and/or papain (for example, COROLASE(copyright) L10 sold by the company Rxc3x96HM ENZYME).
The enzyme complex which hydrolyses the polysaccharides of maize other than starch is SPEZYME CP sold by the company GENENCOR (composed of a complex of cellulase, xcex2-glucanase and pentosanase enzyme activities).
Phytase is, for example, that produced by the company BASF (NATUPHOS).
Glucoamylase is of the OPTIDEX L300 type produced by the company GENENCOR.
The Applicant company has found that the treatment by all these enzymes takes place advantageously in an aqueous solution of maize gluten the dry matter content of which is from 5% to 50%, at a pH from 5 to 9, a temperature ranging from 45xc2x0 C. to 65xc2x0 C. and with a reaction time from 5 hours to 24 hours.
When the Pi/Pt and Na/Nt ratios reach the desired values, the enzyme reactions may be stopped by inactivating the enzymes. To this end, physical means (temperature) and/or chemical means (pH) are used. The reaction medium preferably undergoes heating at 60xc2x0 C.-90xc2x0 C. for a period from 10 minutes to 60 minutes.
The process according to the invention then consists in concentrating the nitrogenous composition thus obtained so that it may optionally undergo an atomisation step.
Insoluble matter is then advantageously removed from the nitrogenous composition which is concentrated by evaporation, either to be kept in the liquid form or to be atomised or dehydrated in a suitable manner.
The composition according to the invention, by virtue of its particular characteristics, has a certain advantage when it is used, advantageously after removal of the insoluble matter, as a microbial growth substance in the fermentation industries.
In particular, this composition is a satisfactory substrate for the production of organic acids by microbiological means.
The Applicant company ascertained that microorganisms could be selected advantageously from the group comprising microorganisms of the Bacillus, Lactobacillus and Pseudomonas type, as will be illustrated below.
Moreover, the nitrogenous composition according to the invention, without the need to remove the insoluble matter therefrom, is of interest to the food industry on account of its nutritional properties and may thus be used as a feedingstuff in compositions intended more particularly for animal feed.